This invention relates generally to fluid processing, and specifically to process flow measurement and control. In particular, the invention concerns measurement techniques for magnetic flowmeters.
Magnetic flowmeters (or mag meters) measure flow by Faraday induction, an electromagnetic effect. The meter energizes a coil to generate a magnetic field across a pipe section, and the magnetic field induces an electromotive force (EMF) across the process flow. The resulting potential difference (or voltage) is measured using a pair of electrodes that extend through the pipe section and into the process flow, or via capacitive coupling. The flow velocity is proportional to the induced EMF, and the volumetric flow rate is proportional to the flow velocity and flow area.
In general, electromagnetic flow measurement techniques are applicable to water-based fluids, ionic solutions and other conducting flows. Specific uses include water treatment facilities, high-purity pharmaceutical manufacturing, hygienic food and beverage production, and chemical processing, including hazardous and corrosive process flows. Magnetic flowmeters are also employed in the hydrocarbon fuel industry, including hydraulic fracturing techniques utilizing abrasive and corrosive slurries, and in other hydrocarbon extraction and processing methods.
Magnetic flowmeters provide fast, accurate flow measurements in applications where differential pressure-based techniques are disfavored because of the associated pressure drop (for example, across an orifice plate or Venturi tube). Mag meters can also be used when it is difficult or impractical to introduce a mechanical element into the process flow, such as turbine rotor, vortex-shedding element or Pitot tube.
Across these applications, there is an ongoing need for improved magnetic flow measurement techniques. In particular, there is a need for reduced-bias flow measurements in high-precision applications subject to process noise effects, including electronic, mechanical and electromagnetic noise contributions.